1. Field of the intention
This invention is related generally to a printer, and more particularly to the improvement of a sheet feed section thereof.
2. Related art
One known sheet feeder used for a conventional printer is disclosed in unexamined Japanese Patent Publication No. Hei. 3-272921 as shown in FIG. 10. The sheet feeder has a hopper table 1 for maintaining a plurality of sheets thereon and three sheet feed rollers 4 for feeding each of the plurality of sheets maintained on hopper table 1. A bottom plate 3, serves as a hopper and is supported by a plurality of springs 2 disposed between bottom plate 3 and hopper table 1, serving as resilient members. Bottom plate 3 is arranged at a portion of hopper table 1 confronting sheet feed rollers 4.
A plurality of sheets S are held on hopper table 1 and are urged toward sheet feed rollers 4 by bottom plate 3, which is itself urged toward sheet feed rollers 4 by the biasing force of springs 2. Each of sheets S is fed toward a print section of a printer (not shown) through the force exerted thereon by the rotation of sheet feed rollers 4.
Since bottom plate 3 supported by springs 2 is arranged at the portion of hopper table 1 confronting sheet feed rollers 4, an edge portion of sheets S confronting and parallel to sheet feed rollers 4 is elevated and urged toward sheet feed rollers 4, so as to extend along sheet feed rollers 4, as shown in FIG. 11. As a result, even if hopper table 1 is not maintained precisely parallel with respect to sheet feed rollers 4, the upper surface of each of sheets S can be maintained in parallel with sheet feed rollers 4. This prevents each of sheets S from contacting less than all of sheet feed rollers 4, and therefore insures that each of sheets S is fed straight and properly by all of sheet feed rollers 4.
While this conventional sheet feeder for a printer has been satisfactory, the following inconvenience has been encountered when sheets S1 whose width is narrower than that of bottom plate 3 are placed on hopper table 1. As shown in FIG. 12, when sheets S1 such as postcards or envelopes or the like whose width is narrower than that of hopper table 1 are placed on hopper table 1 , a side H1 of hopper table 1, holding sheets S1, is maintained at a lower level with respect to a side H2 where no sheets SE are held because sheets S1 force side H1 of hopper table 1 against the bias force of springs 4 while side H2 of hopper table 1 is not so urged. That is, side H2 which holds no sheets S1 rises to a higher level than side H1 which holds sheets S1. Thus, sheet feed rollers 4 come into contact with sheets S1 on an angle with respect to the plane of the sheet S1. As a result, sheets S1 are susceptible to being fed improperly and twisting when being fed. This in turn tends to cause a paper jam because of this defective sheet feed operation.
Thus, it is desired to provide a printer in which even a narrow sheet will be properly fed and will not twist during a sheet feed operation, and in which a paper jam or the like due to this defective sheet feed operation can be prevented.